diff --git a/vncviewer/cocoa.h b/vncviewer/cocoa.h
index e9101f3..0c3ac82 100644
--- a/vncviewer/cocoa.h
+++ b/vncviewer/cocoa.h
@@ -22,6 +22,10 @@
 int cocoa_capture_display(Fl_Window *win, bool all_displays);
 void cocoa_release_display(Fl_Window *win);
 
+typedef struct CGColorSpace *CGColorSpaceRef;
+
+CGColorSpaceRef cocoa_win_color_space(Fl_Window *win);
+
 int cocoa_is_keyboard_event(const void *event);
 
 int cocoa_is_key_press(const void *event);